1. Field of the Invention
The present invention relates to a surface light source device using a light guide plate, and a display device having the surface light source device.
2. Description of Related Art
A liquid crystal display (LCD), which is used for various electronic devices such as a television, a mobile phone, a notebook PC (Personal Computer), and digital camera, generally includes a liquid crystal panel and a backlight irradiating the liquid crystal panel. A light source such as light emitting diode (LED) or cold cathode fluorescent lamp (CCFL) is used for the backlight, and power consumption of the backlight accounts for a large fraction of total power consumed by the display.
A method is proposed as a measure to reduce power consumption of the backlight, where the backlight is divided into several areas, and each area is independently controlled to be turned on or off, so that a selected region is illuminated in accordance with a display region of an image (see Japanese Unexamined Patent Application Publication No. 2001-21863).
A so-called partial drive control method is recently noted, where a backlight is fractioned, and driven in such a manner that an on light-source region and an off light-source region are successively changed in accordance with an image to be displayed. Use of the method may reduce power consumption, and besides, improve contrast, leading to higher image quality. Furthermore, attempt of improving visibility of moving picture display is recently made by using false impulse drive in the partial driving method of the backlight.
A technique is proposed for a backlight structure for achieving such partial drive control, where a plurality of light guide plates are laid, and light sources, which may be independently controlled to be turned on, are arranged for each light guide plate.